Polycystic ovary syndrome (PCOS), the most common endocrine disorder of premenopausal women, is characterized by chronic hyperandrogenism, oligo- or anovulation, obesity, and insulin resistance. Women who have PCOS are at increased risk for glucose intolerance, type 2 diabetes mellitus, and cardiovascular disorders. Recent reports indicate an unexpectedly high prevalence of obstructive sleep apnea (OSA) in women who have PCOS. Alterations in sex steroids and increased visceral adiposity could potentially contribute to the increased prevalence of OSA in this disorder, and there may be strong associations between the presence and severity of OSA and the metabolic disturbances that characterize PCOS. Causal mechanisms in the link between PCOS and OSA remain to be elucidated. Clinicians who manage PCOS patients should be aware of the high prevalence of OSA and should systematically evaluate these women for sleep disturbances.